The present invention relates to the field of semiconductor testing equipment and, more particularly, to the field of probe cards and associated apparatus for semiconductor test systems.
Presently available probe cards make use of conventional printed circuit techniques. These probe cards suffer from use of insulating and structural materials without regard for leakage characteristics. The previous state of the art did not require low leakage probe cards because tester equipment could perform these sensitive tests on only a few device pins, which made it impractical to use probe cards. As the size of devices becomes smaller and smaller, lower current, voltages, and capacitances must be measured. Test system vendors have met this demand with their latest generation of products. However, there has been little corresponding progress in probe card technology.
Crowley, U.S. Pat. No. 4,983,907, is illustrative of the present state of the art. A standard probe card (typically made of FR-4 epoxy plus fiberglass material)has ceramic blades (or some other kind of probe) attached to the center of the probe card for contacting a semiconductor wafer. Wires are attached from the ceramic blades to the probe cards which are then electrically connected to the prober test equipment. The probe cards are of standard sizes so that they may easily mount into standard hardware available from prober vendors. Crowley improves the state of the art by incorporating a guard circuit which reduces somewhat the leakage current.
The present inventors have found, however, that sintered ceramic probe cards are superior to present day FR-4 cards due to their flatness, mechanical rigidity, very high bulk resistivity and imperviousness to moisture. Too, ceramic probe cards have thermal coefficients of expansion that more closely match that of silicon.
Further, the prior art probe cards may be connected to a motherboard. The mode of connection is typically by soldered wires which also provides a leakage path.
The present inventors have proposed an assembly whereby the probe card may be connected to the prober equipment without soldered connections. The resulting assembly is characterized by low leakage currents.
Japanese Pat. No. Application JP63-207146 discloses a ceramic probe card with buried wiring and pins on the back side to connect to the prober equipment. This Japanese reference is deficient in several respects. It does not teach how to reduce the leakage current. Nor does this reference teach an improved method of connecting the probe card to the prober equipment.
Accordingly, it is an purpose of the present invention to have an improved probe card with reduced leakage current.
It is another purpose of the present invention to have an improved apparatus to transition from the probe card to the prober equipment.
It is yet another purpose of the invention to have an improved apparatus to correct for small misalignment between the prober equipment and the wafer.
These and other purposes of the invention will become more apparent after referring to the following description considered in conjunction with the accompanying drawings.